The law of tangled telephone cords

A Queensland-based researcher says his mathematical formula can predict the tangle of your telephone cord, reduce the chance of underwater cables buckling, and explain how DNA molecules coil up inside the nucleus of cells.

Dr David Stump, of the University of Queensland developed the formula, together with two other applied mathematicians, after hearing the woes of underwater cable companies.

While the older heavy copper underwater cables could withstand the pressure of sea currents, the new fibre optic ones, such as those stretching from Auckand to Hawaii, were so light they became easily twisted, especially when they were being laid down. After a certain number of twists, the cables could bend ruining the optical signal.

Dr Stump's formula relates the length of a cord and the number of twists to its final shape. The formula was published last year and Dr Stump has been applying it to a range of practical problems since. The maths applies to any cord-like structure, of whatever size, including DNA.

"Twisting and turning in cords whether they be tiny DNA strands or undersea cables is a natural and unavoidable process," Dr Stump told The Lab.

While twisting and bending is a problem for cables and phone cords it is essential for the effective functioning of cells. Enzymes are constantly adding and removing loops on DNA strands within cells so that required sections are accessible to the particular cell and the rest is tucked away. Luckily, the enzymes can cut and rejoin DNA ends to prevent knots during this 'supercoiling' process.

"This is basic science and is part of a long term effort to understand how DNA coils up inside cells - this is essential knowledge for molecular biologists."

Advice to telephone users in the meantime? "Buy a cordless phone," said Dr Stump, "Or at least make sure that when you flip the receiver over to the opposite hand and ear you don't put a twist in the cord."

The mathematical model was developed by Dr Stump in association with colleague Dr Kevin Gates and the University of Sydney's Dr W Barrie Fraser.